Bacterial or fungal infection has become a worldwide important topic which poses a threat to human health and is given much attention in global medical and health services. It is one of important tools for dealing with bacterial or fungal infection to confer a material or article surface with antimicrobial property to prevent bacterial or fungal growth or multiplication thereon, even to kill bacteria or fungi on the surface. Now, internationally, antimicrobial materials can be divided into four main classes: (1) inorganic antimicrobial agents, for example, nano titanium dioxide, nano silver, nano copper, and their ions; (2) organic antimicrobial agents, for example, quaternary ammonium salts, thiazoles; (3) macromolecular antimicrobial agents, for example, macromolecular quaternary ammonium salts; and (4) natural antimicrobial agents and modifications thereof, for example, chitosan, sorbic acid.
It is the most common for conferring a material or article surface with antimicrobial property to apply a coating containing an antimicrobial agent (for example, nano silver, nano copper and their ions, or others) on the surface. The bacteriostasis or bactericidal effects of nano silver, nano copper, and other heavy metals and their ions are achieved by means of slow release of their metal ions into the environment. However, with usage time increasing, the antimicrobial activity of these materials gradually decreases, until it is eventually lost completely. In addition, microbial variation may be induced, resulting in an increase in the probability of drug resistance. Moreover, the harmfulness of nanomaterials is gradually being recognized and concerned. Organic antimicrobial agents and natural antimicrobial agents have poor heat resistance, which often limits their use ranges. Macromolecular quaternary ammonium salt antimicrobial agents are focused because they can overcome the shortcomings such as high volatility, difficulty in processing, and poor chemical stability of micromolecular antimicrobial agents, have excellent antimicrobial activity, and do not easily permeate into the human skin. For example, Ruowen Fu group [Reactive & functional polymers, 2007, 67:355-366] prepared a series of macromolecular quaternary ammonium salts of methacrylates as antimicrobial agent, having minimum inhibitory concentration(MIC) of 1.56-20 mg/mL. The polymeric antimicrobial agents are also mainly polymeric quaternary ammonium salts and polymeric haloamines, which have undesirable thermal stability. Moreover, in order to obtain a good antimicrobial agent, it is usually required that the antimicrobial agent is water-soluble. So, there is loss in these non-immobilized macromolecular antimicrobial agents, resulting in lack of durability in antimicrobial activity, and also putting a burden on the environment. For example, Lowe et al. [J. Appl. Polym. Sci., 2006, 101:1036-1041] prepared a series of polymeric betaine antimicrobial agents, having minimum inhibitory concentration (MIC) of 1125-2000 ug/mL, which provides a new thought to develop antimicrobial agents. But, they have no reactive functional group that can be immobilized, so that the disadvantage of loss due to release cannot be avoided.
The antimicrobial agent with such release property has at least two adverse factors: (1) the implanted antimicrobial agent has time-dependant release and is lack of persistent antimicrobial activity; (2) the released antimicrobial agent puts a burden on the environment. These factors cannot be neglected and it is inevitable to develop and prepare a green non-released antimicrobial agent. Immobilizing a group with antimicrobial activity onto a material or article surface through chemical bonding can confer the material or article with persistent antimicrobial activity, and also, would not cause contamination on the environment. Madkour [Langmuir, 2009, 25: 1060-1067] prepared a coating with rapid antimicrobial property by reacting a halogen-containing silane with a hydroxyl-containing surface and further employing atom transfer radical polymerization. However, this method has a complicated process and harsh conditions, and is difficult to be industrialized. Saif [Langmuir, 2009, 25:377-379] prepared an organosilicon quaternary ammonium salt antimicrobial agent having persistent antimicrobial activity, and DC-5700 early developed by DOW Corning also belongs to this class. But, the quaternary ammonium salt antimicrobial agent has poor heat resistance, limiting its use range.
It is a new requirement in the development of human society to research and develop a new class of durable antimicrobial agent that can be immobilized, by overcoming the disadvantages present in the field of current antimicrobial agents as described above.